The revamped policy was announced in a letter from Goodell to NFL team owners and calls for a six-week suspension without pay for a first domestic violence offense and a lifetime ban for a second offense.

In his letter, a copy of which was obtained Thursday by SportsNetwork.com, Goodell says he "didn't get it right" last month when he suspended Rice for two games after the Baltimore Ravens running back was arrested on a domestic violence assault charge in February.

Video posted online by TMZ.com showed Rice lifting his then-fiancee out of an Atlantic City casino elevator. The running back avoided prosecution over the incident by entering a pretrial intervention program and has since married the woman.

Goodell suspended Rice for the first two regular-season games and fined him an additional game check for violating the league's personal conduct policy.

The penalty was widely viewed as weak, especially in comparison to another star player's yearlong ban over marijuana use.

Goodell stood by the penalty in public comments he made earlier this month but says in his letter to owners that the league lost opportunity to show a strong stance "on a critical issue."

He says they "allowed our standards to fall below where they should be."

"My disciplinary decision led the public to question our sincerity, our commitment, and whether we understood the toll that domestic violence inflicts on so many families," Goodell says. "I take responsibility both for the decision and for ensuring that our actions in the future properly reflect our values. I didn't get it right. Simply put, we have to do better. And we will."

Goodell says the public response to Rice's suspension "reinforced my belief that the NFL is held to a higher standard, and properly so."

"Much of the criticism stemmed from a fundamental recognition that the NFL is a leader, that we do stand for important values, and that we can project those values in ways that have a positive impact beyond professional football," he says.

"We embrace this role and the responsibility that comes with it. We will listen openly, engage our critics constructively, and seek continuous improvement in everything we do.

"We will use this opportunity to create a positive outcome by promoting policies of respect for women both within and outside of the workplace. We will work with nationally recognized experts to ensure that the NFL has a model policy on domestic violence and sexual assault. We will invest time and resources in training, programs and services that will become part of our culture. And we will increase the sanctions imposed on NFL personnel who violate our policies."

Under the new rules, Goodell says, mitigating circumstances will be taken into account "and more severe discipline will be imposed if there are aggravating circumstances such as the presence or use of a weapon, choking, repeated striking, or when the act is committed against a pregnant woman or in the presence of a child."

Goodell says an offender may petition to be reinstated after a lifetime ban is handed down "but there is no assurance that the petition will be granted."

"These steps are based on a clear, simple principle: domestic violence and sexual assault are wrong. They are illegal. They have no place in the NFL and are unacceptable in any way, under any circumstances," Goodell says. "That has been and remains our policy."

The NFL Players Association said in a statement that it was informed Thursday of the increased penalties and added, "As we do in all disciplinary matters, if we believe that players' due process rights are infringed upon during the course of discipline, we will assert and defend our members' rights."

Goodell says the league will also take the following actions under the enhanced policy:

- It will enhance its training for rookies entering the league and develop new programs for veteran players and other NFL personnel.

- Team and league personnel will undergo training to help them understand and identify risk factors associated with domestic violence and sexual assault.

- NFL wellness programs will be staffed by trained personnel "to provide prompt and confidential assistance to anyone at risk of domestic violence or sexual assault -- whether as a victim or potential aggressor."

- The league will expand its education programs at the college, high school and youth levels that address domestic violence and sexual assault.

- It will work to incorporate domestic violence and sexual assault awareness into its public service work.

"With very few exceptions, NFL personnel conduct themselves in an exemplary way," Goodell says in his letter. "But even one case of domestic violence or sexual assault is unacceptable.

"The reality is that domestic violence and sexual assault are often hidden crimes, ones that are under-reported and under-acknowledged. The steps we are taking will reinforce our commitment to address this issue constructively."

Goodell says the league is also working to maintain strong policies regarding weapons offenses and to strengthen its response to impaired driving offenses.